I'm not really sure what the question is but how about
// assuming str is your JSON string
var obj = JSON.parse(str); // parse the string into an object
var firstObj = obj[0]; // get the first (and only) object out of the array
var fld_id = firstObj.FLD_ID; // you can access properties by name like this
var fld_date = firstObj['FLD_DATE']; // or like this